This invention relates generally to a control system for automatically operating a plurality of controlled mechanisms in a pre-established sequence.
This invention relates particularly to a control system for actuating any number of slide projectors and movie projectors in any desired slide advance and lamp control combination or sequence of the projectors. The invention provides immediate cut of the lamp projectors or two or more variations in the speed of fade-in and fade-out of the lamp projectors and also coordination with an audio program recorded on a magnetic tape.
The sophistication of audio visual presentations has increased significantly within the past few years. The fade-in and fade-out control of projector lamps in particular is a technique often used for blending in and blending out images projected from a plurality of projectors operated in various combinations and in various sequences. Audio programs are also often used in conjunction with the multi-projector visual presentations.
In many situations it is desirable to automate the projector operations and to synchronize the visual presentations with an audio program.
The complexities and difficulties of constructing and operating a control system with multiple projectors, different projector types (e.g. mixes of slide projectors and movie projectors), fade-in and fade-outs of the projector lamps and synchronizing with an audio program increase sharply as the number of projectors increase. And providing different fade-in, fade-out times for different projector lamps produces an additional complexity. As a result, the prior art control systems were limited in the number of projectors which could be coordinated and also were limited in the types of operation which were possible.
U.S. Pat. No. 3,841,746 describes and illustrates a projector control system which operates a plurality of projectors in synchronization with an audio program by means of tone frequency signals prerecorded on one track of a magnetic tape. The system disclosed in the U.S. Pat. No. 3,841,746 works well up to a point. However, this system is limited in the number of control signals that can be utilized because of the problem of harmonics which can be produced when tone frequencies alone are used as the control signal on magnetic tapes. Conventional tape recorders have a usable band width of about 300 Hertz to 5,000 Hertz, and harmonics can be a problem when a relatively large number of tone frequencies are selected as control signals within this fairly narrow band width.